An SMPS (switched-mode power supply) is an electronic circuit that converts power through switching devices that are turned on and off on high frequencies. It also uses storage components like capacitors or inductors to supply power when the switching device is in a non-conduction state.
Switching power supplies are highly efficient and are widely used in various electronic equipment, including computers and other sensitive equipment that need stabilization and efficient power supply. A SMPS is also known as a switch-mode power supply or switching-mode power supply. SMPS's main benefits are its high efficiency, regulated and reliable outputs, small size and lighter, flexibility, and high-power density.
SMPS is used to different power equipment such as sensitive electronics, battery-operated devices, computers, and other equipment requiring higher efficiency. Generally, SMPS are classified in accordance with the type of input and output voltages they carry. The four major categories are:
- AC to DC
- DC to DC
- DC to AC
- AC to AC
The primary isolated AC to DC SMPS consists of:
- Input filter and rectifier
- Output filter and rectifier
- Inverter consisting of switching devices
- Transformer
- Feedback and control circuit
The input DC supply from a rectifier or battery is fed to the inverter where it turns on and off at high frequencies between 20 kHz and 200 kHz by the switching power transistors or MOSFET. The high-frequency voltage current from the inverter is fed to the transformer primary winding, and the secondary AC output is smoothed and rectified to produce the required DC voltages. A feedback circuit monitors the output voltage, and instruction is sent to the control circuit to adjust the duty cycle to maintain the output at the desired level.
Various circuit configurations are known as topologies, with specific and unique characteristics, advantages, and modes of operation, determining how the input power is transferred to the output.
Some essential benefits of using an SMPS:
High efficiency: The switching action of the SMPS means the series regulator element is either on or off. Therefore, little energy is released as heat, and high-efficiency levels can be achieved.
Compact: Owing to higher efficiency and low heat dissipation levels, the switch-mode power supplies are more compact.
Costs: One of the features that make SMPS attractive is the cost. The highly efficient and switching nature means that the heat required to reduce is lower than the linear supplies. This reduces the overall costs of the SMPS significantly. Also, the components used in manufacturing are not very high in costs.
Flexible technology: SMPS technology provides high-efficiency voltage conversions in voltage step-up or "Boost" applications or step down "Buck" applications. This means the technology is highly flexible and be included in various operations.
